Conventional articles of athletic footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for comfortably and securely receiving a foot. The sole structure is positioned between the upper and the ground, and it may include a polymer foam midsole and an outsole. The midsole attenuates ground (or other contact surface) reaction forces to lessen stresses upon the foot and leg. The outsole forms a ground-engaging portion (or other contact surface-engaging portion) of the sole structure and is formed from a durable and wear-resistant material. The sole structure also may include a sockliner or an insole member that is positioned within the void and proximal a lower surface of the foot to enhance footwear comfort.
The upper, in at least some footwear structures, generally extends over the instep and toe areas of the foot, along the medial and lateral sides of the foot, and around the heel area of the foot. In some articles of footwear, such as basketball footwear and boots, the upper may extend upward and around the ankle to provide support for the ankle. Access to the void in the interior of the footwear is generally provided by an access opening. A lacing or other footwear securing system often is incorporated into the upper to selectively increase the size of the access opening and to permit the wearer to modify certain dimensions of the upper, particularly girth, to accommodate feet with varying dimensions and to allow for easy foot insertion and removal. In addition, the upper further may include a tongue that extends under the lacing system to enhance comfort of the footwear and a heel counter to limit movement of the heel.
Various materials are conventionally utilized in manufacturing uppers. The upper of athletic footwear, for example, may be formed from multiple material layers that include an exterior layer, an intermediate layer, and an interior layer. The materials forming the exterior layer of the upper may be selected based upon the properties of wear-resistance, flexibility, and air-permeability, for example. With regard to the exterior layer, the toe area and the heel area may be formed of leather, synthetic leather, or a rubber material to impart a relatively high degree of wear-resistance. Leather, synthetic leather, and rubber materials, however, may not exhibit the desired degree of flexibility and air-permeability for various other areas of the exterior layer of the upper. Accordingly, the other areas of the exterior layer may be formed from a synthetic textile, for example. The exterior layer of the upper may be formed, therefore, from numerous material elements that each imparts different properties to the upper. The intermediate layer of the upper is conventionally formed from a lightweight polymer foam material that provides impact force attenuation and enhances comfort. Similarly, the interior layer of the upper may be formed of a comfortable and moisture-wicking textile that removes perspiration from the area immediately surrounding the foot. In some articles of athletic footwear, the various layers may be joined with an adhesive, and stitching may be utilized to join elements within a single layer or to reinforce specific areas of the upper.